i think they used the phrase nigger in the woodpile in quite a few novels back in the early th century including in a few agatha christie novels such as ten little niggers and dumb witness until around the s when the growth of the civil rights movements rendered the word unacceptable in polite conversation i imagine many tory mps wish they lived back in the s and so tend to read quite a lot of literature from around then so our friend anne no doubt picked it up from there